径向辗环过程尺寸控制的新方法

分析了辗环过程及其变形,建立了径向环件和单阶梯孔件辗环变形过程的数学模型,提出了辗环尺寸控制的新方法,生产应用证明该方法是可行的。     

Ti-4Al-0.005B钛合金大型环件的研制

扼要介绍了Ti 4Al 0 0 0 5B钛合金大型环件的制造过程。对 182 0mm× 14 2 0mm× 2 67mm环件进行了超声波检验 ,并对其实物进行了解剖、测试。试验结果表明 ,该环件弦向、径向和轴向 3个方向的力学性能均达到了零件设计要求的水平。     

楔环受力状态的分析

本文通过实验揭示了楔环联接中楔环的受力状态,从而为楔环的应用和设计提供了可靠的依据。     

5 m径-轴向数控轧环机主要参数的确定

介绍了西安重型机械研究所研制的5 m径-轴向数控轧环机的主要技术参数:轧制力、轧制力矩及轧制线速度的确定方法。现场实测数据表明:理论设计与实际使用吻合。该轧环机是国内最大的轧制铝质环件的设备,在西南铝业公司投产使用,设备运行良好。     

错位环轧工艺

错位环轧工艺是在环件外周的适当位置安置两个辗压轮,同时在环件内孔的两辗压轮与环件接触处之间的近中部位置错位安置一个芯辊,外周的大辗压轮由电动机拖动旋转,它带动环件、芯辊和小辗压轮旋转,构成环轧,外周的两个辗压轮和内孔中的芯辊,在径向发生相向连续的进给运动的过程中,保持内外三个轧辊的错位状态,在此状态下,它们的径向压力难以穿透环件的壁厚,环件壁厚处于未锻透的状态,在轧制过程中,环件的断面面积变化不大,在咬入条件满足时,环件外周及内孔表面的局部连续受压,迫使环件外周表层金属发生轴向流动变形,去充填模具型腔,形成与模具型腔相对应的较复杂的断面形状。     

径轴向轧环机轧环工艺

本文结合我国引进九十年代世界先进水平的径轴向轧环机，详细研究介绍了制订轧环工艺的基础条件、工艺原则、工艺路线及毛坯的优化设计，并对环件产生缺陷的原因进行了分析，提出了对策，以期对我国轧环工艺发展起到促进作用。     

径向辗环变形的数学模型与尺寸控制方式

辗环是生产无接缝环圈的先进技术之一，此分析了辗环过程及变化，建立了径和辗环变形过程的数学模型，以此为据制定的程序，使φ５００型齿轮毛坯辗扩机实现了在线预测智能型尺寸控制，此控制系统投资少，结构简单，性能稳定可靠，在实际生产中使坯件尺寸精度达到：△φ±１ｍｍ保证了稳定生产。     

高锰无磁钢护环锻造特点及锻造工艺

高锰无磁钢护环在加工过程中的锻造工艺要求比较高,本文在针对高锰无磁钢护环锻造特点的基础上,提出了对锻造过程的工艺开发及改进措施.经试制后达到了令人满意的效果,将经过改良后的锻造工艺在工厂里进行实施,降低了高锰无磁钢锻造特点对锻造工艺的影响,提高了护环的内部质量和外观质量,同时也提高了工装的寿命,减少了生产火次和能源的消耗.     

高锰无磁钢护环锻造特点及锻造工艺

高锰无磁钢护环在加工过程中的锻造工艺要求比较高,本文在针对高锰无磁钢护环锻造特点的基础上,提出了对锻造过程的工艺开发及改进措施。经试制后达到了令人满意的效果,将经过改良后的锻造工艺在工厂里进行实施,降低了高锰无磁钢锻造特点对锻造工艺的影响,提高了护环的内部质量和外观质量,同时也提高了工装的寿命,减少了生产火次和能源的消耗。     

The effect of the thermal barrier coating on the displacement instability in thermal barrier systems

Thermal barrier systems are susceptible to instability of the thermally grown oxide (TGO) at the interface between the bond coat and the thermal barrier coating (TBC). The instabilities have been linked to thermal cycling and initial geometrical imperfections, as well as to misfit strains due to both oxide growth and thermal expansion misfit. Numerical simulations are used to investigate the role of the thermo-mechanical properties of the TBC in this instability. It is found that the TBC constrains the deformation, whereupon instabilities develop preferentially in regions where crack-like imperfections either pre-exist in the TBC or are created because of the induced stresses.     

Effect of Extrusion Profile on Surface Microstructure and Appearance of Aluminum Extrusions with Different Fe Contents

Aluminum alloy extrusions with variations in profiles and Fe-rich particles were produced using different extrusion dies and iron contents. A microstructural examination of the extrusion surface shows that the extrusion profile and iron content have a great effect on the size and number of Fe-rich particles, grain size, texture, and fraction of high-angle grain boundaries due to varying localized plastic deformation and temperature in the extrudate. After etching and anodizing, surface imperfections such as grain boundary grooves that influence the final surface appearance are formed on the extrusion surfaces. The severity of grain boundary grooves is found to be directly linked to the number of Fe-rich particles. Hence, the extrusion profile has a dramatic influence on surface imperfections and the appearance of the final anodized extrusions through its effect on the surface microstructure.     

Some Effects of Imperfection Geometry on the Cyclic Distortion of Thermally Grown Oxides

Morphological imperfections on the surface of alloys that form thermally grown oxides (TGO) distort or rumple upon thermal cycling. Models have been developed that predict the dependence of this distortion on oxide growth phenomena and material properties. In the present study, the model is tested in the domain of small (micron-sized) initial imperfections. For this purpose, cyclic experiments have been performed on FeCrAlY substrates using protocols for incorporating small (linear and axi-symmetric) surface imperfections. The experiments revealed a peak rumpling-rate, occurring at characteristic imperfection amplitude of order 1 μm. For smaller imperfections, the growth-rates become immeasurably low. The model accurately reproduces these characteristics. Beyond this additional assessment of the model fidelity, the study has also demonstrated that asymmetric imperfections close during thermal cycling, correcting a misinterpretation that such features are cracks that filled with TGO.     

护环液压胀形时的有限元分析

采用弹塑性有限元分析的方法 ,分析了护环在外补液胀形过程中各个力参数对护环成型形状的影响。     

发电机转子护环变形强化模具的研究

对护环液压胀形模具加载冲头的工作面形线和减力导柱的尺寸进行了讨论。对内增压扩胀护环的装置和双锥面楔块扩孔模具进行了研究。围绕生产中出现的问题 ,提出了改进护环液压胀形和楔块扩孔的措施。     

A numerical assessment of the durability of thermal barrier systems that fail by ratcheting of the thermally grown oxide

Interactions between cracks induced in thermal barrier coatings (TBCs) upon thermal cycling have been calculated. The interactions are motivated by displacement instability in the thermally grown oxide (TGO). The results indicate that the energy release rate G cycles as the temperature changes, with the largest value arising at ambient temperature. It increases on a cycle-by-cycle basis. Cracks that converge from neighboring imperfections exhibit a minimum energy release rate prior to coalescence. Equating this minimum to the toughness of the TBC provides a criterion for coalescence and failure. Imposing this criterion allows the change in crack length upon cycling and the number of cycles to failure to be ascertained.This simulation capability is used to explore various influences on durability. The roles of the heating/cooling rate and the high temperature hold time are assessed, demonstrating substantial variation in durability, especially when the bond coat is relatively soft. The trends from these simulations are compared with experimental results for furnace cycle and burner rig tests. Improvements in the durability upon increasing the high temperature strength of the bond coat and upon decreasing the growth stress in the TGO are established, as well as the influence of the geometric imperfections in the bond coat. Some effects of the thermal expansion misfit between the bond coat and the substrate are explored.     

在护环外补液胀形工艺中护环阻力环的设计方法

提出了形状参数的概念,并推导出了形状参数的计算公式,较好地解决了在外补液胀形过程中护环阻力环设计的问题。     

Failure mechanisms associated with the thermally grown oxide in plasma-sprayed thermal barrier coatings

The microstructure and durability of a thermal barrier coating (TBC) produced by the thermal spray method have been characterized. Upon exposure, the bond coat chemistry and microstructure change by inter-diffusion with the substrate and upon thickening of the thermally grown oxide (TGO). A wedge impression test, in conjunction with observations by scanning electron microscopy, has been used to probe the failure mechanisms. At short exposure times, when the TGO thickness is less than about 5 μm, the growth of the TGO does not affect the crack patterns in the TBC and delaminations induced by wedge impression propagate within the TBC about 30 μm from the interface. An amorphous phase at the splat interfaces promotes this failure mode. As the thickness of TGO increases during exposure, cracks form in the TBC around imperfections at the interface. Moreover, induced delaminations develop a trajectory close to the interface, propagating not only through the TBC but also within the TGO and along the interfaces. A scaling result based on the misfit around imperfections caused by TGO growth has been used to rationalize the critical TGO thickness when the TBC fails.     

Structure and oil retaining capacity of gasar copper fabricated by radial solidification with a combined crystallizer

Porous copper with elongated pores was fabricated by a radial solidification method. The process was carried out in a combined crystallizer under high pressure of a mixture of hydrogen and argon. Pore size, pore length, pore density and porosity of the porous copper were characterized. Furthermore, the oil retaining capacity including oil content and oil efficiency was also evaluated. It is found that porous copper solidified with water-circulated chiller through a thick graphite jacket possesses a gradient structure with increasing pore size, and thus pore density decreases. Also pore length and pore aspect ratio decrease from lateral inwardly, while its porosity is almost uniform. The results show that the porous copper with radial pores has a good oil retaining capacity.     

Characterizing pathological imperfections in macromolecular crystals: lattice disorders and modulations

Macromolecular crystal structure determination can be complicated or brought to a halt by crystal imperfections. These issues motivated us to write up what we affectionately call ‘The Definitive Hitchhiker’s Guide to Pathological Macromolecular Crystals: Lattice Disorders and Modulations’. Perhaps the most challenging imperfections are lattice order–disorder phenomena and positional modulations. Many of these types of crystals have been solved, and progress has been made on the more challenging forms. Diagnostic tools and how to solve many of these problem crystal structures are reviewed. New avenues are provided for approaching the solution of incommensurately modulated crystals. There are a good number of case studies in the literature of lattice order–disorder phenomena and crystallographic modulations that make it timely to write a review. This review concludes with a projected pathway for solving incommensurately modulated crystals, personal views of future directions and needs of the crystallographic community.